Balanced elasticized multifilament yarn



June 20, 1967 N. E. KLEIN ETAL 3,325,988

BALANCED ELASTICIZED MULTIFILAMENT YARN Original Filed Dec. 26, 1961 INVENTORS AR 3.8QLINGER EDG BY NORMA E. KLEIN ATTORN Y United States Patent 3,325,938 BALANCED ELASTICEZED MULTIFILAMENT YARN Norman E. Klein and Edgar Dare Bolinger, Spartanburg,

S.C., assignor's to Deering Milliken Research Corporation, Spartanhurg, S.C., a corporation of Delaware Continuation of application er. No. 162,176, Dec. 26,

1961. This application Mar. 29, 1965, Ser. No. 454,761 (Jlaims. (Cl. 57140) This invention relates to yarns having an elastic nature and to fabrics and garments prepared from these yarns. This application is a continuation-in-part of applications, S.N. 274,358, filed Mar. 1, 1952; 512,871, filed June 2, 1955, now abandoned; 544,521, now U.S. Patent No. 2,919,534; 726,294, filed Apr. 3, 1958, now U.S. Patent No. 3,021,588; and 796,423, filed Mar. 2, 1959, now U.S. Patent No. 3,035,328, and a continuation of application S.N. 162,176, filed Dec. 26, 1961, now abandoned.

It is an object of this invention to provide novel yarns and fabrics and garments, including nylon hose, prepared therefrom having a high measure of elasticity and, in an extended condition, heat set sections of opposite torques.

The above, as well as other objects of the invention, are accomplished by guiding a running length of thermoplastic yarn under a controlled tension through a sharply angular path, heating the yarn so that at least the segment of the yarn transiently disposed at the apex of the sharp angle in the yarn path is at a temperature sufficient to plasticize but insufficient to melt the yarn, cooling the yarn and then reheating the yarn under such conditions as to permit it to assume a distorted configuration. The second heating operation can be performed before or after the yarn is Woven or knitted into fabrics.

The yarn to be elasticized according to the new process can satisfactorily comprise any continuous filamentary strand composed of an organic, hydrophobic, thermoplastic fiber material; however, nylon yarns such as those formed from the reaction product of hexamethylene diamine and adipic acid or from polymers of caprolact-am, are preferred since they can be processed with fewer precautions, are operative through a Wider range of conditions and give a higher degree of elasticization than other types of yarn. The invention can, however, also be employed with polyester yarns, such as those prepared from a reaction product of ethylene glycol and terephthalic acid and sold under the name of Dacron, and the invention can be employed for the elasticization of polyacrylic fibers formed by the polymerization of acrylonitrile or by the co-polymerization of acrylonitrile with a minor amount of another polymeric monomer. Esters of cellulose, such as cellulose triacetate or cellulose diacetate, are also satisfactory and a suitable material of this type is available under the trade name of Arnel. Some yarns give difficulty not so much because of their chemical composition or inherent physical properties but because of their cross sectional configuration. For example, an acrylic fiber sold under the name of Orion has a cross sectional shape resembling the silhouette of a dumbbell and is very diflicult to elasticize by the process of this invention. Yarns wherein the filaments have a generally circular cross section and a smooth surface are most readily employed and give the most satisfactory results.

The denier and filament size of the yarn to be processed may vary within wide limits and almost any of the commercially available yarns within the previously specified class can be satisfactorily employed. As an illustration of the wide range of denier and filament sizes which can be employed, excellent results have been obtained by employing nylon yarns of the following descriptions: 15 denier monofilament; 12 denier 4 filament; 100 denier 34 filament; 70 denier 34 filaments; 200 denier 34 filament;

"ice.

400 denier 68 filament; and 800 denier 51 filament. The denier per filament can range from 1 to 20 or more and the total denier can readily be as high as 2,000 or more. For example, excellent results in preparing a nylon yarn for use in the rug industry have been achieved by processing a filamentary nylon strand having a total denier of approximately 2,000 in the manner previously described.

The yarn, subsequent to passage through the angular course but before the second heating operation, is hereinafter referred to as latently elasticized yarn since, as explained above, it is not until after the second heating operation that the yarn develops its full elastic nature. The filaments in the latently elasticized yarn are characterized by a slightly wavy or coiled appearance when in an untensioned condition and in most instances have a slightly flattened cross section. These linear distortions or coils are generally relatively small in number, occurring in some instances as infrequently as 5 or 6 per inch, and are generally of a relatively large amplitude, having diameters of from about 1 to 3 millimeters in the case of filaments smaller than about 30 denier. For example, in a 15 denier monofilament nylon yarn the coils were found to have an average diameter of 1.85 mm. and in the case of a 70 denier, 34 filament nylon yarn the coils were found to have an average diameter of 1.58 millimeters. The coils are generally of random sized but on occasion yarn will be found in which all of the coils appear to be of a substantially constant size. The curls in any instance are usually temporarily removed by retaining the yarn under only a slight amount of tension. Where the yarn is composed of a plurality of filaments, the coils in adjacent filaments will frequently be found to be running in opposite directions so that the yarn is very bulky in nature.

If the starting yarn is free of torsional stresses and if no torsional stresses are deliberately introduced during processing, the latently elasticized yarn will be substantially free of torsional stresses and only localized torsional stresses resulting from coil formation will be present when in either a tensioned or untensioned condition. The coils are formed such that about 50% of the coils in each filament are in one direction and the remaining half of the coils are in the opposite direction so that there is no over all tendency for the yarn to twist when the coils are removed by tensioning the yarn. This does not mean, however, that there is a reversal point between each individual coil, but to the contrary the yarn will generally carry several adjacent coils running in one direction before a reversal point is encountered, and in some instances the coils will run in the same direction for as much as several inches before reversing their direction. Latently elasticized yarns are, however, characterized by approximately 50% of the coils in each filament running in one direction and 50% in the other only when the filaments are retained substantially free of torsional stresses, and if the yarn is twisted subsequent to processing or if torsional stresses are deliberately introduced during process, the coils will form in a manner to largely relieve these stresses. In other words, by twisting the yarn during processing, a latently elasticized yarn having the coils all running in the same direction can readily be prepared. Of course, as will be apparent to those skilled in the art, the torsional stresses in such instances are reintroduced when the coils in the yarn are removed under tension so that a twisted yarn should not be employed where torsional stresses are objectionable after weaving or knitting.

The appearance of the yarn in its final heat-set form depends upon a number of factors including the conditions under which the second heating operation is performed. 1f the latently elasticized yarn is developed by heating a skein of the yarn in an untensioned condition, the fully elasticized yarn will be characterized by an appearance approximating that of the latently elasticized yarn except that the coils or curls will be smaller in diameter. and more closely spaced, If the yarn filaments are substantially free of torsional stresses in the first instance, the small coils are formed such that about 50% of the coils are in one direction and the remaining half of the coils are in the opposite direction just as in the latently elasticized yarn. The groups of coils will be of random lengths and the coils will be of random pitch. If the yarn filaments are tensioned, there will be substantially no overall tendency for them to twist, but differential transverse stresses, i.e., torque stresses, will be developed which will cause the filaments, when relaxed, to reassume their coiled configurations. The coils will vary in size, but in a well elasticized yarn sample with filaments smaller than about 30 denier the coils will have an average diameter of from 0.2 to 0.9 millimeter and will be so closely spaced as to form a substantially closed helix between reversal points.

The above description of the fully elasticized yarn applies to the greatest extend only when the second heating operation is conducted before the yarn is woven or knitted into fabrics. If the second heating operation is postponed until after knitting or weaving, it will be apparent that closed spiral or coil formations will be inhibited to a large extent. In the case of knitted fabrics, the yarn will attempt to form into coils and in so doing will distort the stitches in the fabric to a marked degree so that the fabric develops a marked elastic nature and a crepe-like appearance. In the case of woven fabrics the second heating operation results in the fabric developing a marked fine grained, tree bark or pebble effect.

It is a feature of the yarns of this invention that it permits the use of elasticized yarns and even of elasticized monofilament yarns without plying or similar measures in the manufacture of knit fabrics, This has been previously impossible, because prior art processes are incapable of producing a stable, elasticized, monofilarnent yarn substantially free of torsional stresses. Knit fabrics formed from non-torsionally stressed yarns according to this invention can be readily distinguished from fabrics formed from conventional elasticized yarns by the coil configuration in the untensioned fabric and by coil behavior upon contraction of the fabric. If one examines a knit fabric formed from elasticized yarns made according to this invention without being torsionally stressed to a high degree, it will be found, when the fabric is stretched to the maximum of its elasticity, that it has a generally normal appearance as if it were made from plain yarns, except that there may be some variation in the size of the interlocking coils of the fabric. When, however, the tension is relaxed and the fabric is allowed to contract in surface area, it will be noticed that a number of things occur. In the first instance, the coils'bow and cup so that the previously flat faces of the coils become arcuate and the individual coils no longer lie in a single plane. In a properly finished fabric formed from a well elasticized sample of yarn,-the bowing of the coils is frequently so pronounced that in most instances the previously flat face of the coil or, in other words, the surface generally defined by the yarn in the periphery of the coil, is bowed through an arc of from 60 to 180. Bowing of the coils tends to be especially pronounced near the base or, in other words, the open part of the coil, butis also generally quite apparent near the top of the coil. Secondly, the coil tends to close so that there is a smaller opening at the base of the coil and the yarn forming the coil extends through a greater arc. In some fabrics a portion of the coils will close completely, and in most well elasticized fabrics the yarn in forming the coil will extend throughan arc of at least about 270 to 300 when the fabric is completely relaxed. A third change noticeable in many instances and particularly in fabrics knit from monofilament yarns, is that the coils become canted with respect to one another so that they are randomly positioned with respect to the plane of the fabric. The random positioning of the coils with respect to the plane of the fabric is a result of the non-torque elasticization procedure of the invention and does not result in a tendency for the courses of the fabric to become skewed with respect to the wales thereof. High torque elasticized yarns must either by plied or knit double carrier with alternating courses or groups of courses of S and Z yarn to prevent or minimize skewing.

The mechanism by which the edge crimping step operates to produce elasticity in the thermoplastic yarn appears to be due to at least three different actions obtained by passing the yarn through theangular course while in a heated condition. The first action is broadly analogous to a phenomenon well known to everyone and which may beobserved by progressively bending a length of ribbon over the blade of a knife or the like to produce a pronounced curl. This action is apparently not dependent upon the yarn being heated as it is passed through the angular course, and, in fact, the action may be noticeably lessened by heating of the yarn as it passes through the angular course.

A second phenomenon which can be observed in some instances is a definite flattening of one side of the fibers and in some instances this flattening occurs to the extent that the yarn fibers actually become crescent shaped in cross section.

A third and most important phenomenon which is ob served is the imparting to the yarn of latent stresses or, in other words, stresses that do not make themselves immediately apparent by changing the linear configuration of the yarn when the tension on the yarn is relaxed. These stresses are referred to as differential longitudinal stresses since their potential action is to cause a differential lengthening or shortening of one cross sectional area of the fiber.

As stated above, the yarn relieves itself of the immediate differential longitudinal stresses, i.e., bending stresses, introduced into it by the edge crimping operation by forming a wavy, spiraled or coiled configuration. The yarn assumes a coil or spiraled configuration because in order for a bending stress to be relieved the yarn must curve and a coil provides a curve of constant radius, thus relieving the bending stress in a constant amount. The number of these spirals or coils is greatly increased when the yarn is given an after heat treatment under relaxing conditions because a latent and greater bending stress, i.e., an additional differential longitudinal stress in the yarn, manifests itself when the yarn is heated. These coils, while running in the same direction for a short series of coils, reverse direction periodically. The reason for this is that for yarn free of torque stresses to form a spiral or coil, without the end of the yarn turning, it must twist about its axis at the point of coil formation and in doing so a torque force is imparted to the yarn. This torque force causes the spiral or coil direction to reverse periodically.

The after heat treatment, in addition to intensifying the spiral or coil formation, also relieves the yarn of its stresses, whether induced by the edge crimping step or by the coil formation. If the yarn is thereafter elongated out of the heat-set, relaxed configuration into a more linear configuration, e.g., by stretching the yarn or suspending a weight on the end of the yarn or on a skein of the yarn, stresses are re-introduced which urge the yarn to return to its fully relaxed, heat-set configuration. These stresses comprise torque stresses, even though the mathematical total of the torque stresses is zero and the yarn is thus a torque-free yarn, with respectto any substantial length thereof, in both its elongated and fully relaxed states.

That these stresses, introduced by elongating or stretching the relaxed yarn, are torque stresses is apparent from the fact that when the heat-set yarn is in a fully elongated or linear configuration, it has no twist in it, other than the conventional low twist present in filament yarns. However, when this yarn is in its relaxed and coiled configuration, it has as high as 30 or more coils per inch. The formation of a spiral or coil in a running length of un twisted yarn without rotating the end of the yarn necessarily and inherently requires that the yarn twist about its axis at that point. Because a yarn twists about its axis only to relieve a torque force it is self-evident that when the yarn is in an elongated and more linear state, which removes some or all of its coils, it has substantial torque forces in it urging the yarn to return to its stress-free, coiled and sectionally twisted state. Because these torque forces in the elongated yarn alternate in opposite directions from coil section to coil section, the net result is that the overall twist of the yarn remains unchanged as it goes into its relaxed state, even though short sections thereof go into a highly coiled and thus highly twisted state.

Thus, such yarn has alternating heat-set sections of op' posite torques, which torques are sufficient to impart stretchability to a fabric or hose knit from the yarn by virtue of their urging the yarn to assume its spiraled or coiled, relaxed configuration.

Reference will now be made to the accompanying drawings in which:

FIGURE 1 is a schematic view in perspective of apparatus suitable for producing edge crimped, latent elasticized yarn.

FIGURE 2 is an enlarged view in perspective of the stitch formation in womens hose knit from 15 denier monofilament nylon yarn edge crimped on apparatus of the type shown in FIGURE 1, the hose then being given the agitated boil-off described herein.

With reference to FIG. 1 of the drawings, there is illustrated a pair of yarn supply means and 11 mounted on a suitable frame or support member, not illustrated. Yarn ends, indicated by the reference numerals 12 and 13, are led from supply packages 10 and 11 through a pair of guide eyes 14 and 15, about a pair of tension regulating devices 18 and 19 and then to a blade assembly generally indicated by the reference numeral 20. The tension regulating devices 18 and 19 serve the dual purposes of removing the fluctuations in tension resulting from the removal of the yarn from the supply packages 10 and 11 and of supplying the yarn ends to the blade assembly 20 at a proper tension, while the guides 14 and are for the purpose of removing the yarn from the yarn supply packages 10 and 11 as smoothly as possible. From the blade assembly the yarn ends are drawn through a portion of the yarn path at 21 which is straight or relatively straight, i.e., a relatively great radius of curvature, and are then brought together and passed through a guide 22 to a pair of driven rolls 23. The two yarn ends are then passed through a guide 24 and to a conventional ring and spindle array generally indicated by the reference numeral 25.

The blade assembly, generally indicated by the reference numeral 20, is here illustrated as comprising an arcuate heater strip 30, preferably formed of stainless steel or the like, which has been bent to a radius of about 4 inches in order to present a slightly curved surface to the yarn. The resistance heater strip is adapted to be heated by means of an electric current passed therethrough and is connected by a pair of electrical conductors 31 and 32 to a variable transformer 33 which is supplied with power from any suitable source, not illustrated, through leads 34 and 35. Mounted on the heater strip 30 by means of a holder 38 is a blade member 39 here illustrated as a common razor blade of a type which is commercially available under a number of trade names such as Schick, Gem, etc. The acuate edge 40 of the blade extends beyond the rear edge of the heater strip 30 a short distance so that the yarn ends 12 and 13 pass in contact with the underside of the heater strip and over the edge of blade 6 39 in an angular path with the edge 40 of blade 39 positioned at the apex of the angular path.

In operation, yarn ends 12 and 13 are threaded through the apparatus in the manner previously described to rolls 23 and the rolls placed in operation so that both yarn ends can be passed together through guide 24 to the spindle array 25. Before further operation of the rolls 23, the adjustable transformer 33 should be set to give sufficient energy to heater element 30 so that it is heated to the desired temperature. With the heater element 30 at the desired temperature and with the apparatus properly threaded, the rolls 23 and the spindle array 25 are placed in operation and thereafter the apparatus requires no further attention unless an end breaks or a yarn supply becomes depleted. By this arrangement two single ends are processed to give them a potentially elastic nature and are plied together for forming a two-ply yarn. It will be understood, however, that the yarn ends can be collected singly if desired and that conventional apparatus which does not impart a twist to the yarn can be employed for the collection thereof.

It will be readily apparent to those skilled in the art that apparatus of the type described can readily be constructed by modification of a conventional spinning or twister frame. In either instance all that need be added is the blade assembly 30, the tension devices 18 and 19 and in some instances the guide member 22. In the case of a twister frame, the rolls 23 can constitute the conventional yarn feed means and in the case of a spinning frame the rolls 23 can constitute the delivery pair of the drawing rolls. It will also be apparent that a single heater strip of considerable length can serve a multiplicity of blades spaced at selected intervals corresponding to each posi tion of the frame. In such an arrangement it is usually desirable for the heating element to be insulated, for example, with foam glass insulation, between the various blade positions to reduce the heat loss.

In the type of apparatus described, the yarn is forced through an abrupt change of direction by passing the same over an acuate edge and while this is presently the most convenient method of accomplishing the desired result, it will be apparent that the yarnmay be caused to undergo the required abrupt change of direction in other ways.

With particular reference to FIGURE 2 of the drawings, there is illustrated a knit fabric according to this invention formed from monofilament yarn. For ease of illustration the fabric is shown stretched to an extent short of the maximum although it will be understood that the distinguishing characteristics of the fabric are most pronounced when the fabrics are in a completely untensioned condition. Canting of the coils with respect to each other and with respect to the plane of the fabric is illustrated by the coils indicated by the reference numerals 50 and 51. This characteristic is among the first to disappear upon stretching of the fabric and as illustrated in the drawings, the coils have been, to a large extent, drawn into the plane of the fabric. The closed nature of the coils is illustrated, for example at 52, and it will be noticed that majority of the other coil are more nearly closed than might be expected in a conventional knit fabric although the coils have, in most instances, been opened to some extent by stretching of the fabric. Bowing of the coils is clearly evident, for example at 53. This is presently believed to be perhaps the most important characteristic, as far as the elasticity of the fabric is concerned, and is generally the last to disappear as the fabric is stretched.

To transform the latently elasticized yarn to the fully elasticized yarns of this invention, it is necessary to relax the stresses created in the yarn as a result of its being passed through the angular path in a heated condition and as previously mentioned, it is an advantage that the relaxation of these stresses can be postponed until after the yarn has been woven or knitted into a fabric. Relaxing the stresses in the yarn after it has been formed into a fabric, however, requires special precautions since it is quite difi'icult to make certain that the yarns are under a sufficiently low tension that the stresses are, at least to an appreciable degree, positionally relaxed rather than internally relaxed or heat'set. In other words, conditions must be such that the relaxation of the latent stresses causes the yarn to assume or attempt to assume a convoluted or irregular linear configuration and if the fabric is rapidly heated, for example, by plunging the same into a hot water bath, the internal stresses in the yarn will be for the most part internally relaxed since the bulk of the fabric and the presence of adjacent courses of yarn Will prevent the yarn from assuming the distorted linear configuration necessary for maximum elasticity. It has, however, been found that gradually raising the temperature of the fabric favors the positional relaxation of the stresses in preference to the internal relaxation thereof and for this reason a preferred procedure comprises gradually raising the temperature of the fabric, for example, by introducing the same into a cold Water bath and thereafter slowly heating the bath to an elevated temperature. It has also been found that agitation of the fabric during the heating operation favors positional relaxation of the internal stress presumably because the yarns in the fabric, over at least a portion of their length, are generally in a near tensionless condition during part of the agitation cycle.

A preferred procedure for developing a high degree of elasticity in fabrics woven or knitted from the latently elasticized yarn comprises introducing the fabric into a bath at a temperature of no more than about 100 F. and preferably at a temperature of no more than about 80 F. The temperature of the bath is then raised with agitation until the bath has an ultimate temperature of at least about 140 F. and preferably above about 180 F. If desired, the bath can be raised to its boiling point, which will be approximately 212 F. The heating of the bath should be gradual and the rate of temperature increase should not exceed about 3 to 4 F. perminute until the bath is at a temperature of about 140 F. and should not exceed about 5 to 6 F. per minute thereafter. The temperature of the bath may be raised at a much slower rate if desired and as a general rule the more gradual the heating, the higher the degree of elasticity in the finished product. Agitation of the bath should be initiated before or concurrently with heating and can advantageously be as violent as is possible without injury to the knitted or woven material. The agitation should be conducted continuously through at least the first stages of the heating operation or at least until the bath is at a temperature of about 140 F. and in most instances it is advantageous to continue the agitation throughout the heating operation and for 5 or more minutes after the temperature of the bath is at the highest value to which it i to be raised.

The particular means for providing the agitation does not appear to be important, provided the agitation is sufliciently severe in nature. The fabric may be mechanically agitated, or it may be subjected to the action of jets of steam, compressed air or to sonic or supersonic vibrations. In most instances satisfactory agitation can be accomplished by means of a standard rotary wash wheel machine either of the vertical agitator or horizontal cylinder type, and in the case of small knit articles, satisfactory results can also be achieved by the use of a hosiery dye machine. The agitation should be such that the fabric is thoroughly flexed at least 2 or 3 times a minue even when the temperature rise is exceedingly gradual and with a reasonably rapid temperature rise, i.e., 2 to 5 F. per minute, the fabric should be flexed 10 to times or more per minute. For this reason better results are generally obtained when using a hosiery dye machine if the speed of rotation is doubled, for example, increased to 12 r.p.m. for a pound machine. In the case of small knit articles it is also generally advantageous to place the articles loosely in a bag to prevent damage during the agitated heating operation.

If the full elastic nature of the latently elasticized yarn is to be developed before the yarn is formed into fabrics, agitation and a gradual temperature rise are not required since the yarn can readily be placed in a substantially tensionless condition and when in this condition the positional relaxation of the stresses in the yarn prevails over the internal relaxation of the stresses to the extent that an excellently elasticized yarn is obtained even if the temperature rise is very rapid. In this instance, the heating can be conducted by overfeeding a single end of the potentially elastic yarn into a heated fluid or into contact with a heated surface so that the yarn is allowed to coil freely at the time its temperature is elevated. A high temperature is not required and satisfactory results can generally be obtained if the yarn is heated to a temperature of only about F. although a temperature of from about to 400 F. is generally preferred. Care should be exercised to insure that the yarn at the time it is heated is under as little tension as possible, and if the tension in the yarn is allowed to rise above about .004 to .01 gms./ denier, good elasticizing may not be obtained. If the tension in the yarn is at a proper level, the yarn assumes a highly convoluted linear configuration almost immediately so that the heating need not be continued for more than 1 or 2 seconds. As an alternative to the above procedure, the yarn can be formed into skeins and the skeins immersed in a hot liquid or passed through a heated chamber to result in the yarn developing its full elastic nature. When the yarn is fully elasticized by either of these procedures before its formation into fabric, no special manipulations of the woven or knitted fabrics are required, although it is generally advantageous to weave or knit the yarn in a loose manner so that upper relaxation of the tension necessary for weaving or knitting, the yarn i free to curl or'kink to provide the desired effect.

Example I A full fashioned hosiery machine is employed to knit ladies hosiery from nylon yarns prepared according to the process of US. application, Ser. No. 274,358, filed Mar. 1, 1952, employing a 15 denier monofilament yarn in the boot, 30 denier 10 filament yarn in the welt and 30 denier 10 filament yarn in the splice. The hose are removed from the knitting machine and placed in loosely knit cotton bags, 20 pairs to the bag. The bags of hosiery are then entered into a 25 pound hosiery dye machine geared to rotate at twice its usual speed or in other words geared to rotate at 12 revolutions per minute. Cold Water at a temperature of 90 F. is entered into the machine, 0.1 pound of a sodium soap (Lux Flakes) are added and the machine is placed in operation. After 20 minutes, the temperature of the bath is gradually raised approximately 2 F. per minute until the bath is at the temperature of 120 F. and thereafter the temperature of the bath is raised approximately 4 F. per minute until the bath is at a temperature of 180 F. Agitation is continued for an additional 5 minutes at 180 at the end of which time the bath temperature is dropped and the hosiery thoroughly rinsed in clear water. Without removing the hosiery from the dye machine, a dye bath is entered and the hose dyed in a conventional manner. After dyeing, the hose are thoroughly extracted, removed from the bath and boarded through a normal cycle of 1% minutes at 250 F. The hosiery prepared in this manner have a vary attractive dull satin-like appearance and a degree of elasticity which permits them to be readily stretched through 3 or 4 size ranges. In wear tests it is found that the hose outwear conventional stockings by a considerable margin.

Example II On a single feed circular knit machine there are knit a plurality of pairs of womens hosiery utilizing nylon yarn prepared by the method of co-pending U.S. application 274,358 and employing 20 denier 7 filament in the boot and 40 denier 13 filament in the welt, heel and toe. The hose are removed from the machine, placed in loose knit cotton bags with 15 pairs of hose to each bag and entered into a 25 pound hosiery dye machine geared for 12 revolutions per minute. Cold water at a temperature of 70 is entered into the machine and 0.1 pound of a sodium soap (Lux Flakes) are added for good detergency. The machine is placed in.operation and after approximately 20 minutes the temperature of the bath is raised at the rate of 4 degrees per minute to a temperature of 120 F. and thereafter at a rate of 6 F. per minute until the bath is at the boil. The hose are then rinsed, excess moisture removed by extraction and the hose removed from the cotton bags and placed on boarding forms. The hose are passed through a preboarding cycle of one minute at 270 F. and thereafter removed and dyed in a conventional manner. The dyed hose are then final boarded through a cycle of 1% minutes at 220 F. The finished hose display a very dull satin-like appearance when off the leg and a very sheer even appearance when worn. In fact, the Sheerness of the hose when worn compares favorably with that of 15 denier monofilament nylon hose made from conventional yarns. The hose display a good measure of elasticity and 3 or 4 sizes are adequate to cover the entire range.

Example Ill On a 24 feed, 12 cut, interlock Wildman Jaquard TAI knitting machine there are knit in tubular form, two interlock sweater bodies from elasticized yarn prepared generally according to the procedure of US. application, S.N. 274,358 except that it was, following the edge crimping operation and before being collected, overfed 22% to a heating zone maintained at 363 F. The two sweater bodies are then separated, labeled A and B, and placed in separate open-mesh, water-permeable bags.

Sweater A is placed in a Najort wheel type washer containing water at a temperature of about 80 F. and run for 30 minutes. At the end of this time a detergent composition (Orvus High Temp Granules) is added in an amount sufficient to produce noticeable suds, and the temperature of the bath is raised to 120 F. in 15 minutes with the machine in continuous operation. The temperature of the bath is then raised from 120 F. to 180 F. in ten minutes and operation of the machine is continued for an additional 5 minutes with the temperature of the bath held constant at 180 F. The sweater body is then rinsed in cold water for five minutes and tumble dried at 140 F. for 30 minutes.

Sweater body B is placed in a Najort washer containing water at 180 F. and sufficient detergent to result in noticeable foam, and is run for 30 minutes with the temperature held constant. The sweater body is then rinsed in cold water for five minutes and tumble dried at 140 F. for 30 minutes. The procedure employed with sweater body B is conventional and is for comparison purposes only.

Following drying, each of the sweater body samples are sectioned for testing purposes. Sweater body A Was found to have a single layer thickness of 66.8 mils, a double layer thickness of 131.0- mils (Standard A.S.T.M. thickness test except using a 2 inch diameter foot), and was found to weigh 5.43 ounces per square yard. Sweater body B was found to have a single layer thickness of 60.1 mils, a double layer thickness of 118.8 mils and to weigh 5.24 ounces per square yard.

That which is claimed is:

1. A continuous thermoplastic latently elasticized filament characterized by the presence of latent crimp-forming stresses along the length thereof, said stresses urging said filament to assume crimp configurations in alternating, random sections of opposite torques, said stresses being sufficiently balanced that said filament is substantially free of torsional stresses caused by said crimp-forming stresses.

2. The filament of claim 1 wherein about half of the latent crimp-forming stresses urge said filament into crimp configurations arranged in one direction and the remaining latent crimp-forming stresses urge said filament into crimp configurations arranged in the opposite direction.

3. The filament of claim 1 wherein the latent crimpforming stresses urge said filament into crimp configurations of random sizes.

4. The filament of claim 3 having a slightly flattened cross-section.

5. The filament of claim 3 wherein the cross-section is crescent-shaped.

6. The filament of claim 1 being further characterized by the presence of a heat-latent differential longitudinal stress along the length thereof, the effect of which is to cause a differential lengthening or shortening of one cross sectional area of said filament upon the application of heat thereto.

7. The filament of claim 6 wherein the heat-latent differential longitudinal stress cooperates with the latent crimp-forming stresses to intensify crimps along the length thereof upon the application of heat to said structure.

8. A thermoplastic latently elasticized filamentary structure characterized by the presence therein of both immediate and heat-latent differential longitudinal stresses, both of which urge said structure, under certain conditions, to assume crimp configurations in alternating random sections of opposite torques along the length of said structure so that the total of torsional stresses in said filamentary structure is substantially zero; said immediate differential longitudinal stresses being manifested by the presence of said crimp configurations in said structure merely by removing tensional forces from said yarn; said heat-latent differential longitudinal stresses being manifested by an intensification of said crimp configurations formed by release of said immediate differential longitudinal stresses upon the application to said structure of sufficient heat to release said heat-latent stresses, said intensification of said crimp configurations taking place by virtue of a susbtantial differential lengthening or shortening of one cross-sectional area of the filamentary structure.

9. The filamentary structure of claim 8 wherein the crimp configurations formed by the relaxation of said immediate differential longitudinal stresses comprise coils having an average diameter of from about 1 to about 3 10. The filamentary structure of claim 9 wherein said heat-latent differential stresses tend to intensify said coils to an average diameter of from about 0.2 to about 0.9

11. A continuous thermoplastic latently elasticized filament characterized, in an untensioned condition, by a plurality of crimps along the length thereof, said crimps being arranged in alternating, random sections of opposite torques, the mathematical total of torsional stresses in said filament being substantially zero; said filament being further characterized by the presence of heat-latent differential longitudinal crimp-forming stresses along the length thereof, which stresses tend to intensify the crimps present in said filament.

12. The filament of claim 11 wherein said crimps comprise coils.

13. The filament of claim 12 wherein the coils are of random size and pitch.

14. The filament of claim 12 wherein the coils have an average diameter of from about 1 to about 3 millimeters.

15. The filament of claim 14 wherein the heat-latent differential stresses are sufficiently strong as to reduce the average diameter of said coils to from about 0.2 to about 0.9 millimeter.

16. A multifilament yarn comprising a plurality of filaments as in claim 12, the coils in adjacent filaments running in opposite directions so that said yarn is very bulky in nature.

17. The filament of claim 12 wherein about 50% of the 1 l 1 2' coils are arranged in one direction and the remaining References Cited coils are arranged in an opposite direction so that there UNITED STATES PATENTS is no overall tendency for said filament to twist When the coils are removed by tensiomng 2,919,534 r 1/1960 Bollnger et al. 28-1 18. A fabric comprising the filament of claim 12. 5 FOREIGN PATENTS 19. A knitted fabric containing the filament of claim 5158 297 12/1943 Great Britain 20. A fabric comprising the filament Of claim 12, said STANLEY N. GILREATH Primary Examiner. fabric being constructed in such a manner that the heatlatent differential longitudinal stresses of said filament are 10 PETRAKES: Exammerfree to intensify the coils of said filament.

Dedication 3,325,988.N0rmwn E. Klein and Edgar Dare Bolinger, Spartanburg, SC). BALANCED ELASTICIZED MULTIFILAMENT YARN. Patent dated June 20, 1967. Dedication filed June 22, 1971, by the assignee, Deem'ng Milliken Research Gowpomtion. Hereby dedicates to the Public the entire terminal portion of the term thereof falling on and after Jan. 5, 1977.

[Oflieial Gazette September 14, 1.971.] 

1. A CONTINUOUS THERMOPLASTIC LATENLY ELASTICIZED FILAMENT CHARACTERIZED BY THE PRESENCE OF LATENT CRIMP-FORMING STRESSES ALONG THE LENGTH THEREOF, SAID STRESSES URGING SAID FILAMENT TO ASSUME CRIMP CONFIGURATIONS IN ALTERNATING, RANDOM SECTIONS OF OPPOSITE TORQUES, SAID STRESSES BEING SUFFICIENTLY BALANCED THAT SAID FILAMENT IS SUBSTANTIALY FREE OF TORSIONAL STRESSES CAUSED BY SAID CRIMP-FORMING STRESSES. 